Neutron capture therapy with Sulfur-33, similar to boron neutron capture therapy with Boron-10, is effective in treating some types of tumors including ocular melanoma. The key point in sulfur neutron capture therapy is whether the neutron beam flux and the resonance capture cross section of $$^{33}\hbox {S(n},\alpha )^{30}\hbox {Si}$$ 33S(n,α)30Si reaction at 13.5 keV can achieve the requirements of radiotherapy. In this research, the authors investigated the production of 13.5 keV neutron production and moderation based on an accelerator neutron source. A lithium glass detector was used to measure the neutron flux produced via near threshold $$^{7}\hbox {Li(p,n)}^{7}\hbox {Be}$$ 7Li(p,n)7Be reaction using the time-of-flight method. Furthermore, the moderation effects of different kinds of materials were investigated using Monte Carlo simulation.